1. Field of the Invention
The present invention relates to an image processing apparatus adapted for generating reproduced images with special effects, and also to an image processing method, especially to a method in which image processing operations are performed by using memory.
2. Description of Background Information
Conventionally, it was necessary to use an image processing apparatus having a complex construction in order to produce special effects in color pictures, especially to produce an after-image effect.
On the other hand, image-processing operations such as the size-reduction, and the enlargement of an image, or the generation of movement of image, can be performed in the following manner for instance. At first a video signal is digitized, and is stored into a memory, and the digitized video signal is read-out from the memory by designating addresses which are different from those used at the time of writing.
Furthermore, the after-image effect can be obtained by writing only parts of a video signal representing images with movement into the memory and outputting the said parts and the other parts which were already stored, in combination. In order to obtain the after-image effect, it is conceivable to detect the portion of the video signal corresponding to an object with movement, and to write only this portion. However, with this method, it is necessary to separately provide a memory for storing data of one field long for example, in order to detect the portion which has moved, thereby creating a problem that the structure of system becomes complicated.
On the other hand, the frequency of the color subcarrier signal of the video signal in NTSC system for example, is set at a frequency as indicated by the following equation, in which the frequency of horizontal synchronization is expressed by f.sub.H, and the frequency of vertical synchronization is expressed by f.sub.V : ##EQU1##
Therefore, if the composite video signals written in arbitrary periods are combined and outputted, that will result in the loss of the continuity of the color subcarrier signal in the output video signal, so that color pictures can not be properly obtained.
On this account, an image processing apparatus as shown in FIG. 1, designed for producing color pictures properly, was devised.
In this figure, a composite video signal is supplied to a Y-C separation circuit 1 so that it is separated into a luminance signal Y and a color signal C. The luminance signal Y is, after being converted to a digital signal by means of an A/D converter 2, supplied to a memory 3. The color signal C is supplied to a color demodulator 4, in which color difference signals R-Y and B-Y are demodulated. These color difference signals R-Y and B-Y are converted to digital signals by means of A/D converters 5 and 6 respectively, and subsequently supplied to the memory 3.
The memory 3 is controlled variously by operations such as the address control by means of a memory controller 7, and the digitized luminance signal Y, color difference signals R-Y, B-Y are written into the memory 3. The luminance signal Y, the color difference signals R-Y and B-Y, after read-out from the memory 3, are supplied to D/A converters 8, 9 and 10, so that those signals are converted to analog signals. The color difference signals R-Y and B-Y, after being converted to the analog form, are supplied to a modulator 11', in which a color subcarrier signal is modulated, to form the color signal C. This color signal C is supplied to an adder circuit 12', in which the luminance signal Y supplied from the D/A converter 8 are added thereto, so that a composite video signal is produced.
In the above explained circuit, there are drawbacks that the construction of the apparatus is complicated, and the quality of the picture is degraded after passing through the demodulation circuit and the modulation circuit.